Nate Skeen
Origin of Life on Earth
 Processes of spontaneous origin
o abiotic synthesis and accumulation of small organic molecules or
monomers
o synthesis of polymers from monomers
o aggregation of abiotically produced molecules into droplets, called
protobionts, (jumble of organic molecules like RNA inside a membrane or
membrane like structure)
o self-replicating molecules
o synthesis of organic molecules
o water tends to depolymerize molecules (makes it difficult for molecules to
become polymers) but is necessary for life), but is necessary for life
o joining of these monomers into polymers
o origin of heredity (may have been under way before ‘droplet’ stage
 Miller & Urey
o Conducted experiment that simulated hypothetical conditions of Early
Earth
o Two flasks, one for the ocean and the other for the atmosphere, were
connected into a loop with glass tubes
o The ocean flask was placed above a heating source which would warm the
liquid water to evaporation
o Water vapor would then travel through the tubing system until it reached
the second flask, simulating atmosphere.
o The atmosphere flask contained water vapor, methane, ammonia, and
carbon monoxide, as well as two electrodes that would spark to simulate
lightning
o The water vapor would then travel through a condenser and be reduced to
liquid water, which would travel through a sampling probe and back into
the ‘ocean’ flask to restart the cycle
o After one week of continuous cycling, Miller and Urey reported that 10%15% of the carbon in the system was in the form of organic compounds
like amino acids, sugars, lipids, and some building blocks for nucleotide
bases
 Comets
o Comets can carry organic compounds
o Earth was bombarded with comets and asteroids 4 billion years ago
o Impact could help polymerize amino acids into polypeptides
 Locations of synthesis
o Space
 Scientists have created amino acids in low pressure and low
temperature conditions
o Alternating wet/dry conditions
 Seashores
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Drying clay particles could have catalyzed reactions to form
organic molecules
 stromatolites
o Near volcanoes
 Eruptions spit out water vapor, gases, and minerals which could
form organic compounds
 Raw materials + heat could have provided conditions for amino
acids and sugars
o Deep oceans
 thermal vents release heated water that picks up minerals along the
way
Properties of RNA that could’ve allowed it to play a role in abiogenesis
o RNA can self replicate
o RNA can act as a catalyst (ribozyme), helping reactions
Coacervates and Microspheres in origins of life
o Coacervate
 A tiny spherical droplet of assorted organic molecules
(specifically, lipid molecules) which is held together by
hydrophobic forces from a surrounding liquid.
o Microsphere
 Protein protocell (RNA)
 Polypeptides dissolved in hot water can form small spherical
structures when dried and cooled
 Providing a membrane-enclosed volume which is similar to that of
a cell
 Can grow and contain a double membrane which undergoes
diffusion of materials and osmosis.
Prokaryotic contribution to oxygen rich atmosphere
o 3.5 bya bacteria developed the ability to photosynthesize
o Helped convert iron dissolved in ocean water, into precipitates of iron
oxide = rust-colored layers of rock
o Waste production of photosynthesis is oxygen
o Photosynthetic bacteria proliferated and produced more and more oxygen
Endosymbiotic theory and eukaryotes
o Eukaryotes came about as a result of symbiotic relationships between
prokaryotes
 One engulfed by other
 i.e. chloroplasts and mitochondrion